It Is known that road usage by vehicles continues to increase, year on year. Increased road usage causes many problems, such as increased congestion, longer travel time, higher travel costs, increased air pollution, increased accident risk, etc. In order to cope with this steady increase, solutions are required to better manage vehicle road usage. A possible solution is to construct new roads, which is unlikely to happen on a large enough scale. A further solution is to reduce traffic and/or provide alternative transportation options, neither of which is viable in most practical scenarios.
A further solution that is being widely researched and developed is the use of intelligent traffic (or transportation) systems (ITS). Intelligent transportation systems (ITS) are applications which provide, for example, services relating to transport and traffic management and enable various users to be better informed and make safer, more coordinated, and ‘smarter’ use of transport networks. ITS is also being considered to facilitate autonomous driving. Although ITS may refer to all modes of transport, ITS is defined in EU Directive 2010140/EU (7 Jul. 2010) as systems in which information and communication technologies are applied in the field of road transport, including infrastructure, vehicles and users, and in traffic management and mobility management, as well as for interfaces with other modes of transport.
Various forms of wireless communications technologies have been proposed for intelligent transportation systems. IEEE 802.11p is an approved amendment to the IEEE 802.11 standard to add Wireless Access In Vehicular Environments (WAVE™), a vehicular communication system. It defines enhancements to 802.11 (the basis of products marketed as Wi-Fi™) required to support ITS applications. The 802.11p standard, as with other Wi-Fi™ standards such as 802.11a, 802.11g, 802.11n, 802.11ac, etc., is packet based and each packet consists of preamble symbols and data symbols. This includes data exchange between high-speed vehicles and between the vehicles and the roadside infrastructure. Such a range of communications is often referred to as ‘vehicle to everything (V2X)’ communications.
Today's vehicles are also equipped with many wireless services to receive radio and television broadcasting and to support communications technologies, such as cellular phone and global positioning system GPS™ for navigation.
The vehicle-to-vehicle communication systems in Europe and USA make use of the IEEE802.11p standard, which operates in bends: ITS-G5A, ITS-G5B and ITS-G5D: 5.855-5.925 GHz. The Japanese ARIB STD-T109 standard dedicates the operating frequency bend of 755.5-764.5 MHz ITS, with a centre frequency of 760 MHz and an occupied bandwidth of 9 MHz or less. Typical ITS networks contain vehicles with at least two communication units, each able to establish communication with other cars or devices near the road and at the same time communicate with each other.
In most practical applications, it is known that in order to support communication in all directions around the car at least two V2X communication units are required. This is because, in practical situations, first the rooftop of a vehicle is not horizontal but has an inclination; and secondly many rooftops are not made completely from metal but contain glass or plastics, thereby causing imperfections in the transmitted and received communication signals. In the widely-used shark fin antenna design, multiple antenna structures will be closely spaced together influencing one and others' characteristics. These effects result in a non-omnidirectional radiation pattern, which results in at least two V2X communication units (and two antennas separated physically as much as possible) being typically required to achieve a best or at least an acceptable performance. A skilled artisan will appreciate that a sufficient spatial separation is required for obtaining as much as possible isolation between the two feeding ports and to uncorrelate the antenna parameters.
In order to manage communication between the at least two communication units within the vehicle, the vehicle includes an Ethernet connection that links the at least two communication units. This Ethernet connection involves more than introducing a cable, as the in-vehicle system requires extra integrated circuits (ICs) to support wireline transceiver functionality, synchronization, managed voltage supplies to ensure electromagnetic interference (EMI) rejection is within specified limits, etc. Transmitters and receivers are typically implemented as integrated circuits where the particular functions are implemented as hardware blocks, with software running on (digital signal) processors, or a combination of hardware and software. Thus, the in-vehicle communication system to supplement V2X communication has resulted in being an additional complex and expensive system.